I bought a Windows 7 Home Premium but I kept getting the blue screen error and it was very unstable so I gave it to my friend and went back to vista. I activated the Win 7 when I had it installed. Now he's getting this message that he has to activate the windows and since it was activated on my computer it's not letting him activate. How can I deactivate it so my friend can activate it? Do I have to install it on my computer again and then do something?

Tell your friend to use the phone option and call Microsoft. Only takes a few minutes and should not be a problem. Good directions here: How to Activate Windows 7 by Phone Rich

To amplify:There's no explicit de-activation. You are supposed to uninstall Win7 from the old system, but if it's like XP or Vista, there are no Microsoft checks for that.Phone activation is the right way to deal with it.

Hi Omairk, First you should remove the Windows 7 partition from your computer and then ask your friend to contact Microsoft Activation Center directly to activate Windows 7 via phone. For more details, please refer to the following KB article. How to contact a Microsoft Product Activation Center http://support.microsoft.com/kb/950929 Good luck! Andy

It already is uninstalled from my computer, we haven't tried doing the phone activation, will do that now. Thanks.